The present invention relates to a reciprocating, two-stroke internal combustion engine that can return most of the exhaust heat to the engine cycle to do work. Thermal regeneration is the capturing of waste heat from a thermodynamic cycle (or a heat engine operating on some thermodynamic cycle), and the utilization of that energy within the cycle or engine to improve the cycle or engine""s performance. This is commonly done with many heat engines including Stirling engines, gas turbines, and Rankine cycle devices. In a gas turbine the exhaust heat coming out of the exhaust is transferred to the air leaving the compressor and going into the combustor. This way it is not necessary to add as much heat (fuel) in the combustor to raise the air temperature to the desired turbine intake temperature. This means that the same work is accomplished but less fuel is used. The automobile and truck gas turbines use rotating regenerators to transfer energy from the exhaust gases to-the-compressed air.
The approach taken by previous inventors who attempted to incorporate regeneration into reciprocating internal combustion engines was to try to regenerate using a movable heat exchanger low-pressure side attached to the movable wall. The most successful design is Two Stroke Regenerative Engine, Warren (2000, U.S. Pat. No. 6,116,222). The drawback to this design is moving the mass of the regenerator, and difficulty cooling the power piston. Other differences exist between that engine and the-regenerated engine disclosed herein. All of these are discussed in greater detail in the section entitled xe2x80x9cDescriptionxe2x80x9d.
The xe2x80x9cTwo Stroke Internal Combustion Enginexe2x80x9d is an engine that operates on a very efficient cycle. To obtain this good efficiency the xe2x80x9cTwo Stroke Internal Combustion Enginexe2x80x9d is an engine where very little heat is rejected from the engine because compression is carried out at close to constant temperature. This is accomplished by multistage intercooling. After compression, heat that is obtained from the heat exchanger at near constant pressure is added to the compressed air. Before the pressure starts to drop, heat is added at high temperature by injecting fuel and burning it in a slowly expanding volume, complete expansion then takes place. And finally, heat is transferred by the heat exchanger from the exhaust to the air coming from the compressor exit, then the cycle repeats.
The engine of this invention can be operated on a cycle that approaches the maximum efficiency possible. The compression is cooled. With enough additional compressors the compression process approaches constant temperature compression. This process rejects the least amount of heat possible. There is no known way to reject less heat. The heat that is recovered from the exhaust by the heat exchanger is then added at close to constant pressure. Then before the pressure drops, heat is added at high temperature by injecting fuel and burning it in a slowly expanding volume. This process adds close to the most amount of heat possible. Complete expansion takes place.
The engine is a two-stroke, internal combustion, reciprocating engine made up of a number of similar working units. Each working unit is comprised of cylinder 12 that is closed at one end by cylinder head 4 and contains power piston 18 that is connected to power output shaft 22. Movable wall 11 is provided to take in the working air, to move the working air through heat exchanger high-pressure side 10, to move the working air through heat exchanger low-pressure side 40, and to push the exhaust out of cylinder 12. Displacer 9 is provided to move the working air through cooler 17. Movable wall 11 and displacer 9 can move between power piston 18 and cylinder head 4. The means to accomplish this movement at the appropriate times during the engine""s operating cycle are: cam 30 moving moveable wall cam follower 32 that is attached to movable wall 11 and cam 30 moving displacer cam follower 33 that is attached to displacer 9.
The advantages of the Warren Cycle Internal Combustion Engine are:
It can be operated with little heat rejected and what is rejected is rejected at the lowest temperature possible for a hot air heat engine.
It can be operated with a large amount of heat added at a very high temperature.
The thickness of movable wall 11 can be such that the compression and the expansion volumes are separated. The heat from one does not effect the other.
All parts of the engine that are hot stay hot. All parts of the engine that are cold stay cold. There is no cycling of any parts of the engine between hot and cold.
The air compressed into cooler 17 stays compressed in cooler 17 and waits for the next cycle.
The compressed air in heat exchanger high-pressure side 10 stays compressed in heat exchanger high-pressure side 10 and waits for the next cycle.
As many compressor cooling systems as desired may be added to the engine. The more compressor cooling systems an engine has, the closer its compression equals the efficient constant temperature compression.